Extra long/extra deep ......

Try House of Bath. They do deep fitted sheets. Nit sure about the extra long though.

JL do Super King sized sheets that might fit. Often they are in the bargain bin, I suspect there's not many sales!

Dunelm do extra deep sheets and not expensive.

I'd buy plain flat sheets - ordinary double - and fit by hospital corners.

They wouldn't be long enough, surely...?

Linencupboard.co.uk

linencupboard.co.uk might help

Ive never been able to buy well fitted sheets for my deep mattress, they just kept slipping off the corners and on the sides never actually went under the mattress fully so Ive gone back to plain flat sheets. It was the same with mattress covers they dont fit either so I use a flat sheet to cover the mattress.

Dunelm

Out of Eden are very reasonable, although they are hotel suppliers they seem to offer single items.

To be honest to get generous sizes I think you'd have to pay a bit. I bought fitted sheets from "Interior Designers" on line
Lovely quality and aS high a thread count as I could afford. They last for ever.

Markies do deep fitted sheets too.

Thanks everyone - I did check out all suggestions.
The problem is that I need the length to be more than 190cm and the depth to be at least 25cm - it looks as though I may be heading for Ikea as they have the right size at a price I can afford.

Victoria Linen co do all sorts of custom made sheets, not cheap, but good quality. I bought a 3'6" x 6'6"" electric bed and then had to search for sheets.

Be careful when buying from IKEA, they do sell lots of different sizes, double check, we bought a " standard single" mattress for a " standard single bed" only to find it didn't fit, closer examination showed completely different sizes and we had to take the mattress back. To be fair, it did have the sizes on but we didn't realise this at the time. They did take it back and the assistant helpfully wrote down where we could find the exact right mattress for the bed( it confusingly had the same Swedish name as the incorrect one) so they must be used to this confusion. The sheets also come in different widths / lengths for their mattresses .

I have 2 single beds pushed together as one superking and I use a superking flat sheet. I bought my latest ones on line. They were mega long as my beds are regular length so should fit 6'6" bed. I also cover the two beds with an old king size duvet as a mattress topper. Great way to store spare duvet and bed super comfy!

Oops- obviously misread the start of this thread. Must be too early on a Sunday.

The White company sales?
M&S do deep. I use super king for the same problem.

TJC do a single fitted sheet and pillowcase in a very soft 100% cotton for £9.99+pp.My mattress is 6ft3in and 10in deep and the sheet is plenty big enough and with good elastication that secures it right under the mattress all round. Look online under "Accessories" then "Home Textiles".

Try www.soakandsleep.com they have a sale on for the next couple of days. I have always found them excellent.

Dunelm Mill do various sizes of sheets. I got extra deep for my kingsize bed.

Have you looked on here?
linencupboard.co.uk

Just googled it for you, Amazon and Dunelm do them.

Ikea sheets are good. They also come up big. I have a super king bed and the fitted sheet would take a slightly larger mattress